Laser engraving is used to personalize or to convey indicia on an identification document, including creating images and/or information (e.g., text and graphics) on the identification document. Engraving is a secure way to impart indicia to a document, because the indicia becomes part of the document.
For the purposes of this disclosure, identification documents are broadly defined and may include, e.g., credit cards, bank cards, phone cards, passports, driver's licenses, network access cards, employee badges, debit cards, security cards, visas, immigration documentation, national ID cards, citizenship cards, social security cards, security badges, certificates, identification cards or documents, voter registration cards, police ID cards, border crossing cards, legal instruments or documentation, security clearance badges and cards, gun permits, gift certificates or cards, labels or product packaging, membership cards or badges, etc., etc. Also, the terms “document,” “card,” and “documentation” are used interchangeably throughout this patent document. Identification documents are also sometimes referred to as “ID documents.”
Identification documents can include information such as a photographic image, a bar code (e.g., which may contain information specific to the person whose image appears in the photographic image, and/or information that is the same from ID document to ID document), variable personal information (e.g., such as an address, signature, and/or birth date, biometric information associated with the person whose image appears in the photographic image, e.g., a fingerprint), a magnetic stripe (which, for example, can be on a side of the ID document that is opposite a side with a photographic image), and various designs (e.g., a security pattern like a printed pattern comprising a tightly printed pattern of finely divided printed and unprinted areas in close proximity to each other, such as a fine-line printed security pattern as is used in the printing of banknote paper, stock certificates, and the like). Of course, an identification document can include more or less of these types of features.
One exemplary ID document comprises a core layer (which can be pre-printed), such as a light-colored, opaque material, e.g., TESLIN, which is available from PPG Industries) or polyvinyl chloride (PVC) material. The core can be laminated with a transparent material, such as clear PVC to form a so-called “card blank”. Information, such as variable personal information (e.g., photographic information, address, name, document number, etc.), is printed on the card blank using a method such as Dye Diffusion Thermal Transfer (“D2T2”) printing (e.g., as described in commonly assigned U.S. Pat. No. 6,066,594, which is herein incorporated by reference), laser or inkjet printing, offset printing, etc. The information can, for example, comprise an indicium or indicia, such as the invariant or nonvarying information common to a large number of identification documents, for example the name and logo of the organization issuing the documents.
To protect information printed on a document, an additional layer of transparent overlaminate can be coupled to the document to cover the printed information. Illustrative examples of usable materials for overlaminates include biaxially oriented polyester or other optically clear durable plastic film.
One type of identification document 100 is illustrated with reference to FIG. 8. The identification document includes a substrate/core 120 perhaps with a protective or decorative overlaminate 112 or 112′. The identification document 100 optionally includes a variety of other features like a photograph 104, ghost or faint image 106, fixed information 108 (e.g., information which is generally the same from ID document to ID document), signature 110, other machine-readable information (e.g., bar codes, 2D bar codes, information stored in optical memory) 114, variable information (e.g., information which generally varies from document to document, like bearer's name, address, document number) 116, etc. The document 100 may also include overprinting (e.g., DOB over image 106), microprinting, graphics, seals and background-patterns (all not shown).
Of course, there are many other physical structures/materials and other features that can be suitably interchanged for use with the laser engraving techniques described herein. The inventive techniques disclosed in this patent document will similarly benefit these other documents as well.
We disclose herein laser-engraving methods to enhance identification documents.
Lasers (e.g., CO2 or YaG lasers) can be used for marking, writing, bar coding, and engraving many different types of materials, including plastics. Lasers have been used, for example, to mark plastic materials to create indicia such as bar codes, date codes, part numbers, batch codes, and company logos. It will be appreciated that laser engraving or marking generally involves a process of inscribing or engraving a document surface with identification marks, characters, text, tactile marks—including text, patterns, designs (such as decorative or security features), photographs, etc.
One way to laser mark thermoplastic materials involves irradiating a material, such as a thermoplastic, with a laser beam at a given radiation. The area irradiated by the laser absorbs the laser energy and produces heat, which causes a visible discoloration in the thermoplastic. The visible discoloration serves as a “mark” or indicator, and usually appears gray. Lasers can also be focused to burrow through or burn away a material to create a hole or opening.
One inventive color laser engraving method involves providing a card stock including a top surface layer and one or more sub-layers. The sub-layers include various colors and arrangements of inks, dyes or pigments. (The terms “ink,” “dye” and “pigments” are hereafter used interchangeably). We provide openings (e.g., holes) in the surface layer to reveal one or more sub-layers. The openings allow different sub-layer color inks to convey a color image.
A digital watermark can be conveyed in the engraved, color image. For example, one or more digital watermarks are embedded in an image or text. The embedded image or text is used as a master pattern to guide laser engraving. A resulting engraved image or text will include the one or more digital watermarks, since the watermarks are transferred along with the image and text.
In other embodiments, digital watermarks are pre-embedded into a document by changing intensity or luminance of color ink provided in or on a sub-layer. The sub-layer's color changes become evident as openings are created in a surface layer. Changing or removing the digital watermark is difficult since the watermark is physically part of the card through laser engraving. This digital watermark can provide, e.g., an inventory control number for card stock, which is inherently embedded in the card stock and becomes detectable after the laser engraving process. In some implementations our “pre-embedded” watermark is embedded in addition to a watermark conveyed with an engraved image.
One aspect of the invention is a method of digitally watermarking a document that is to receive laser engraving. The method includes: providing one or more sub-layers, the one or more sub-layers to include coloration; providing variations in the coloration in terms of at least one of color intensity and color contrast, the variations conveying a digital watermark including a plural-bit message; and arranging a surface layer over the one or more sub-layers. The digital watermark is machine-readable after laser engraving.
Another aspect of the invention is an identification document. The identification document includes a sub-layer including a plurality of inks arranged in a grouping. The sub-layer includes repeated instances of the grouping. The identification document further includes a surface layer adjacently arranged with the sub-layer. The surface layer obscures at least a majority of the repeated instances of the grouping. The identification document further has a plurality of openings in the surface layer, wherein at least some portions of some of the repeated instances of the grouping are perceptible through the plurality of openings to convey an image or text.
Yet another aspect of the present invention is a method of color laser engraving a document. The document includes a multi-layer structure including a surface layer and one or more sub-layers. The one or more sub-layers include coloring. The method includes receiving the document; and selectively providing openings in the surface layer with a laser to expose one or more of the sub-layers. The coloring is perceptible through the openings.
The foregoing and other features, aspects and advantages of the present invention will be even more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.